Studies on functional and morphological aspects in human multinodular simple goiter tissues

Distinguishing Recurrent Thyroid Cancer from Residual Nonmalignant Thyroid Tissue Using Multiphasic Multidetector CT

BACKGROUND AND PURPOSE

During thyroidectomy incomplete resection of the thyroid gland may occur. This complicates the imaging surveillance of these patients as residual thyroid needs to be distinguished from local recurrence. Therefore, the purpose of this study was to determine if multiphasic multi-detector computed tomography (4D-MDCT) can differentiate residual nonmalignant thyroid tissue and recurrent thyroid carcinoma after thyroidectomy.

MATERIALS AND METHODS

In this retrospective study, Hounsfield unit values on multiphasic multidetector CT in precontrast, arterial (25 seconds), venous (55 seconds), and delayed (85 seconds) phases were compared in 29 lesions of recurrent thyroid cancer, 29 with normal thyroid, and 29 with diseased thyroid (thyroiditis/multinodular thyroid). The comparison of Hounsfield unit values among lesion types by phase was performed using ANOVA. The performance of Hounsfield unit values to predict recurrence was evaluated by logistic regression and receiver operating characteristic analysis.

RESULTS

All 3 tissue types had near-parallel enhancement characteristics, with a wash-in-washout pattern. Statistically different Hounsfield unit density was noted between the recurrence (lowest Hounsfield unit), diseased (intermediate Hounsfield unit), and normal (highest Hounsfield unit) thyroid groups throughout all 4 phases (P < .001 for each group and in each phase). Dichotomized recurrence-versus-diseased/normal thyroid tissue with univariate logistic regression analysis demonstrated that the area under the receiver operating characteristic curve for differentiating benign from malignant thyroid for the various phases of enhancement was greatest in the precontrast phase at 0.983 (95% CI, 0.954-1), with a cutoff value of ≤62 (sensitivity/specificity, 0.966/0.983) followed by the arterial phase.

CONCLUSIONS

Recurrent thyroid carcinoma can be distinguished from residual nonmalignant thyroid tissue using multiphasic multidetector CT with high accuracy. The maximum information for discrimination is in the precontrast images, then the arterial phase. An optimal clinical protocol could be built from any number of phases but should include a precontrast phase.

Etiopathology, clinical features, and treatment of diffuse and multinodular nontoxic goiters

Goiter, an enlargement of the thyroid gland, is a common problem in clinical practice associated with iodine deficiency, increase in serum thyroid-stimulating hormone (TSH) level, natural goitrogens, smoking, and lack of selenium and iron. Evidence suggests that heredity also has an important role in the etiology of goiter. The current classification divides goiter into diffuse and nodular, which may be further subdivided into toxic (associated with symptoms of hyperthyroidism, suppressed TSH or both), or nontoxic (associated with a normal TSH level). Nodular thyroid disease with the presence of single or multiple nodules requires evaluation due to the risk of malignancy, toxicity, and local compressive symptoms. Measurement of TSH, accurate imaging with high-resolution ultrasonography or computed tomography, and fine-needle aspiration biopsy are the appropriate methods for evaluation and management of goiter. This review discusses the clinical presentation, diagnostic evaluation, and treatment considerations of nontoxic diffuse and nodular goiters.

Relevance of iodine intake as a reputed predisposing factor for thyroid cancer

Iodine is a trace element that is essential for the synthesis of thyroid hormone. Both chronic iodine deficiency and iodine excess have been associated with hypertrophy and hyperplasia of follicular cells, attributed to excessive secretion of TSH. This may be associated to thyroid cancer risk, particularly in women. Experimental studies have documented thyroid cancer induction by elevation of endogenous TSH, although in a small number of animals. Iodine deficiency associated with carcinogenic agents and chemical mutagens will result in a higher incidence of thyroid malignancy. Inadequate low iodine intake will result in increased TSH stimulation, increased thyroid cell responsiveness to TSH, increased thyroid cell EGF-induced proliferation, decreased TGFbeta 1 production and increased angiogenesis, all phenomena related to promotion of tumor growth. Epidemiological studies associating iodine intake and thyroid cancer led to controversial and conflicting results. There is no doubt that introduction of universal iodine prophylaxis in population previously in chronic iodine-deficiency leads to a changing pattern of more prevalent papillary thyroid cancer and declining of follicular thyroid cancer. Also anaplastic thyroid cancer is practically not seen after years of iodine supplementation. Iodine excess has also been indicated as a possible nutritional factor in the prevalence of differentiated thyroid cancer in Iceland, Hawaii and, more recently, in China.

IN CONCLUSION

available evidence from animal experiments, epidemiological studies and iodine prophylaxis has demonstrated a shift towards a rise in papillary carcinoma, but no clear relationship between overall thyroid cancer incidence and iodine intake.

Moléstias associadas à carência crônica de iodo

Fundamentalmente, a glândula tiróide, face à carência de iodo, se adapta por incremento da captação deste halogênio, aumenta a sua massa glandular (bócio), induz secreção preferencial de T3 e eleva a síntese e liberação de TSH. Os exames laboratoriais e de imagem permitem a comprovação dos mecanismos adaptativos. A iodúria permite avaliação quantitativa do grau de carência iódica. Em algumas populações, coexiste a influência de bocígenos naturais presentes nos alimentos consumidos localmente. O cretinismo endêmico é síndrome neurológica e endócrina que conduz o indivíduo a quadro severo de rebaixamento mental e surdo-mudez. No Brasil, as moléstias associadas à carência de iodo foram sempre avaliadas por inquéritos nacionais em escolares. A correção da deficiência de iodo se faz pela adição de iodato de potássio ao sal de consumo humano. Várias leis e decretos foram elaborados tentando aperfeiçoar o sistema universal de iodação do sal, que, mais recentemente, foi aprimorado e tornou-se mais eficiente em propiciar iodo a toda população brasileira.

C-cells in colloid goiter

PURPOSE: The aim of this investigation was to quantitatively evaluate C-cells in colloid goiters, analyzing 36 thyroids that were obtained through thyroidectomy from 24 patients with goiter and 12 normal glands from adult patients without thyroid disease, which were used as the control group. MATERIAL AND METHODS: On average, 6 different thyroid areas were sampled and labeled by immunohistochemistry with a monoclonal anticalcitonin antibody, utilizing the avidin-biotin-peroxidase complex. C-cells were counted in fields measuring 1 square centimeter, and the mean number of cells per field was then calculated. Data were statistically analyzed using the Mann-Whitney test. RESULTS: In the colloid goiter group, the number of C-cells ranged from 0 to 23 per field, while in normal controls they ranged from 20 to 148 per field. CONCLUSIONS: These results demonstrate a significant decrease of C-cell number in the colloid goiter group compared with control group, indicating that the hyperplastic process is restricted to follicular cells, to the detriment of C-cells, which probably cease to receive trophic stimuli.